U.S. Pat. No. 2,371,227 issued to A. Y. Dodge on Mar. 13, 1945 shows a fluid clutch wherein hydraulic fluid is circulated through a gear pump to provide power transmission between a gear and gear housing. A valve in the liquid circuit obstructs liquid flow to produce a hydraulic lock. The present invention involves a variation on the system shown in U.S. Pat. No. 2,371,227, comprising a metering valve that produces a gradual throttling of the liquid flow through the gear pump, whereby the gear and gear housing gradually come to the same speed in a shock proof fashion. The metering valve is regulated by the pressure in the pump outlet chamber so that pump action increases the outlet chamber and simultaneously produces throttling movement of the metering valve.